A PROCESS AND DEVICE FOR MEASUREMENT OF SPECTRAL INDUCED POLARIZATION RESPONSE USING PSEUDO RANDOM BINARY SEQUENCE (PRBS) CURRENT SOURCE

摘要

A process and device for measurement of spectral induced polarization response of subsurface over a wide band of frequencies (0.03 Hz to 100 Hz) using pseudo noise current source, is provided. (Pseudo Random Binary Sequence current source).The measurement setup employs a current source (500VA) and a computer controlled real time correlator for excitation of the subsurface. The current from the source is reversed through the grounded electrodes in a Pseudo Random Binary Sequence (PRBS) and the computer based receiver essentially computes Auto (input-input) and Cross (input- output) correlation estimates in the field. The collected data (time series) is transformed into frequency domain (DFT) in order to obtain the phase spectrum. The receiver has a provision to stack data for an improved S/N ratio. Measurements taken in laboratory using simple RC network, which simulates the subsurface, are accurate.Accuracy of measurement is better than 2 % in Band-I (0.031 - 2 Hz) and 1 % in Band- Il (2-100 Hz) respectively.